1. Technical Field
The present invention relates to a light-emitting diode with layer construction of nitride semiconductor (InXAlYGa1-X-YN, 0≦X, 0≦Y, X+Y≦1), especially, first to a light-emitting diode capable of making its light emission uniform and of improving its life, and secondly to a light-emitting diode capable of improving light outgoing toward the observation side.
2. Description of Related Art
A light-emitting diode with the layer construction of nitride semiconductor is widely used as a high-luminance pure green LED, blue LED in various fields such as a full color LED display, a traffic light, and a backlight.
Generally, these LEDs have layer construction, in which an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are successively laminated on or above a substrate such as sapphire. Further, a p-side electrode is provided on the p-type nitride semiconductor layer, and an n-side electrode is provided on the n-type nitride semiconductor layer. For example, when the p-side electrode and the n-side electrode are provided in the same plane side, the p-side electrode is positioned on the p-type nitride semiconductor layer, and the n side electrode is positioned on an exposed n-type nitride semiconductor layer, which is formed by removing a part of the p-type nitride semiconductor layer, active layer, and n-type nitride semiconductor layer by etching etc. Furthermore, in order to supply a current, a conductive member such as a gold wire or various materials of solder is connected to each electrode. Various electrode arrangements of such an LED have been proposed (see reference 1, for example). Moreover, in order to improve light outgoing, various kinds of LED construction are proposed (see reference 2, for example).
However, it is not easy to make light-emission wide and uniform in an LED, even though the p-side current diffusing member is provided in the p-side electrode. That is a first problem. On the other hand, when each electrode is deformed or enlarged in order to make light-emission wide, this causes too high a concentration current area. Consequently, this causes not only insufficient efficiency of light-emission efficiency but also reduction of the life.
Furthermore, when an opening portion is provided in an area which is usually a light-emission area in order to improve light-emitting efficiency, this reduces device characteristics such as high LED resistance. That is a second problem.
Reference 1: Japanese Laid-Open Publication Kokai No. 2000-164930
Reference 2: International Publication number WO01/41219